The biological significance of several new microbial vitamin-coenzyme relationships are to be studied. We propose to isolate, characterize, and determine the structure of: (1) a new cofactor which is required for CO2 reduction, (2) chromophoric Factor 430 and Factor 342, (3) an unknown growth factor for Methanobacterium mobile. We propose to study the microbial chemistry of these new factors to determine their relationship to coenzyme functions. These factors are fractionated from extracts of methanogens, and the possible role of these factors in the enzymic catalysis of animal, plant, and other microbial systems will be studied. We propose to continue studies on the biochemical synthetic pathway of coenzyme M and its analogs.